Hip arthroplasty has been an effective way to treat a hip joint trauma, ageing, inflammation and pathological changes, to alleviate patients' pains, to help a patient restore motion ability and to improve patients' living quality. The physical function of an artificial hip joint is achieved through relative motions between an artificial femoral ball head and an artificial acetabulum.
The existing artificial acetabulums typically includes a combinational type and a whole type. A combinational type artificial acetabulum substantially includes a metal acetabular cup (acetabular outer liner) mechanically combined with an Ultra High Molecular Weight Polyethylene (UHMWPE) liner or a ceramic liner. There are small gaps between the metal acetabular cup and the liner, which results in wearing particles due to micro-motion in use. These particles may be swallowed by the macrophage and results in osteolytic factors and further leads to osteolysis around the artificial hip joint, which increases the risk of postoperative complication, such as pain, and collision, dislocation of a femoral ball head, aseptic looseness or sink of the artificial hip joint. Further, during a minimally invasive surgery, it is difficult to install a combined artificial acetabulum due to a narrow operation space.
A whole type artificial acetabulum may overcome problems existing in the above-mentioned combinational artificial acetabulum, such as an insecure combination between the metal acetabular cup and the liner, and unsatisfactory anti-drop and anti-rotation performance. However, the whole type artificial acetabulum including a metal acetabular cup and an UHMWPE liner may limit motion degree of a patient's hip joint due to a high thickness of the UHMWPE as required. An artificial femoral ball head may only have a diameter of about 28 mm. Therefore, an artificial femoral stem (neck) is likely to collide with the edges of the acetabulum, which may result in looseness, and even dislocation of a femoral ball head. A whole type all-metal artificial acetabulum may produce metal ions which are dissolved out due to frictions between the artificial acetabulum and a surface of an artificial femoral ball head. The metal wearing particles (like aluminum, titanium, cobalt or chromium) may be carcinogenic, and may adversely affect the function of the hemopoietic system and intelligence level of the patient. Accordingly, the whole type all-metal artificial acetabulum is not applicable for pregnant women, children, and people who suffer from hematological diseases or hepatic and renal dysfunction. A whole type all-ceramic artificial acetabulum has an excellent histocompatibility, without releasing of potentially toxic metal ions and together with a high surface hardness and excellent wear resistance; however, the ceramic still has drawbacks such as low fracture toughness, bad impact-resistance bearing capacity, and insecurity in biomedical application.
So far, there is no effective method to avoid the problems of wearing particles, dissolution of metal ions and brittle fracture in the existing artificial acetabulum during the biomedical application.
For a long time, cobalt-based or titanium-based alloy has been widely used as a material of the artificial femoral ball head. However, problems same as the whole type all-metal artificial acetabulum mentioned above still exist. To solve the problems, both U.S. Pat. No. 6,241,773 and Japanese patent No. 2579212 disclosed an artificial femoral ball head made of high-purity aluminia ceramic. However, the aluminia ceramic has disadvantages of high brittleness, low fracture toughness, and had impact-resistance bearing capacity. The aluminia ceramic femoral ball head is likely to fracture in vivo. Accordingly, the aluminia ceramic itself is not an ideal material for each component of an artificial hip joint. Chinese patent application No. CN1386067A, filed by Matsushita Electric Industrial Co., Ltd. in 2005, discloses an artificial hip joint made of composite ceramic including zirconia-aluminia. The composite ceramic includes a matrix-phase of zirconia in a tetragonal crystal structure and a second-phase of aluminia particles dispersed the matrix-phase. Compared with the high-purity aluminia, the problems of fracture toughness is improved significantly, however, the mechanical strength (hardness), wear resistance and stability of phases are decreased, which may not support a durable and stable hip joint movement in a human body. Therefore, there is still a huge gap between the existing artificial hip joint and the desire of lifetime service, and it is far from meeting requirements of the majority of patients.